/// <summary>Used to cast the return value of a native call to something useful.</summary>
/// <remarks>This is better than a C# cast because it will produce a decent error message
/// if there are problems and it will convert native IntPtr objects to the corresponding managed
/// object.</remarks>
public static T To <T>(this object value)
{
// If the value is null then return some form of null.
if (value == null || value.Equals(IntPtr.Zero))
{
if (typeof(T).IsValueType)
{
throw new InvalidCastException("Value is null");
}
else if (typeof(T) == typeof(NSObject))
{
return((T)(object)new NSObject(IntPtr.Zero));
}
else if (typeof(NSObject).IsAssignableFrom(typeof(T)))
{
return((T)Activator.CreateInstance(typeof(T), BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public, null,
new object[] { IntPtr.Zero }, null));
}
else
{
return(default(T));
}
}
// If T matches the value type then just cast value to that type.
Type type = value.GetType();
if (type == typeof(T))
{
return((T)value);
}
// If T is bool then allow value to be an sbyte.
if (typeof(T) == typeof(bool) && type == typeof(sbyte))
{
return((T)(object)((sbyte)value != 0));
}
// If T is NSObject, a derived class, or IntPtr then do a lookup and
// return the correct managed class.
if (type == typeof(IntPtr) || typeof(NSObject).IsAssignableFrom(typeof(T)))
{
IntPtr instance = IntPtr.Zero;
if (type == typeof(IntPtr))
{
instance = (IntPtr)value;
}
else
{
instance = (IntPtr)(NSObject)value;
}
NSObject obj = NSObject.Lookup(instance);
if (obj == null)
{
return(default(T));
}
else if (typeof(T).IsAssignableFrom(obj.GetType()))
{
return((T)(object)obj);
}
else
{
throw new InvalidCastException("Can't cast from " + obj.class_().Name + " to " + typeof(T) + ".");
}
}
throw new InvalidCastException("Can't cast from " + type + " to " + typeof(T) + ".");
}